Successions of the zoobenthos of Dubossary reservoir under the impact of hydro power engineering

Abstract

In 1954, the Dubossary reservoir was formed on the middle Dniester. Changes in the hydrological regime in the early years led to a reduction in zoobenthic species from 190 to 75, mainly litho- and psammoreophiles. In the 1970s, the species composition increased to 130 and to 160 in the 1980s. The total abundance was of 18000 ind./m2, the biomass of the “soft” zoobenthos was up to 40 g/m2. After the construction of the Novodnestrovskoye PSP in 1984, the flow rate decreased in the Dubossary reservoir, silting and overgrowing with macrophytes intensified. The successions of benthos continued, it became more pelophilic with a predominance of the oligochaete-chironomid complex and mollusks. The number of species decreased to 120 by 1990, and now it has increased to 169, and invasive species have appeared. Dreissena dominates in the malacofauna. The number of “soft” benthos, which is 94% formed by the oligochaete-chironomid complex, in 2010-2021 amounted to 3450 ind./m2 with a biomass of 13.37 g/m2.